Field of the Invention
The present invention relates to a controller for an electrophotographic image forming apparatus.
Description of the Related Art
Electrophotographic image forming apparatuses that deflect a light beam (laser beam) emitted from a laser light source by a rotating polygonal mirror and scan a photosensitive member by the deflected laser beam to form an electrostatic latent image on the photosensitive member are known. In such image forming apparatuses, typically image data generated by a control board, in which a system controller which is an integrated circuit is mounted, is transmitted to a laser driving board in which a laser driver for driving a laser light source is mounted, and based on the received image data the laser driver drives the laser light source.
Also, image forming apparatuses of a multi-beam type that comprise as light sources a plurality of light emitting elements for emitting a plurality of light beams that scan in parallel different lines respectively on the photosensitive member in order to realize an acceleration of image forming speed and an increase in resolution of images are known. There is a problem in that in such multi-beam type image forming apparatuses, in conjunction with an increase in the number of light emitting elements, the number of signal lines (including printed wirings and cables) between the system controller and the laser driver increases. With respect to this, Japanese Patent Laid-Open No. 2011-31451 describes a technique for performing serial transmission of data between a system controller and a laser driver, and the number of signal lines can be reduced by using serial transmission.
There are cases in which a laser driver, which has a laser driving board comprising a conversion circuit for converting image data to PWM signals or has a conversion circuit depending on manufacturing costs or the like built-in, is mounted in an image forming apparatus, and cases in which a laser driving board which does not comprise such a conversion circuit is mounted. Therefore, it is necessary to change a design of a system controller to match a configuration of a laser driver or a laser driving board mounted in an image forming apparatus regarding whether or not to generate a PWM signal on the system controller side and perform a serial transmission of the PWM signal to the laser driver. Meanwhile, it is desirable to realize a system controller that is independent of such a configuration of a laser driver or a laser driving board.